1. Field of the Invention
The present invention relates to a step attenuator. It specifically relates to a step attenuator used within the microwave band.
2. Prior Art
An ideal feature of the step attenuator is that the difference between loss of the entered signal transmission in respective attenuation mode and through-mode (non-attenuation mode) stays constant over all the frequency bands. However, the ideal feature cannot be attained by using the conventional step attenuators. Specifically, the difference between the transmission loss of the entered signal in the respective attenuation mode and through-mode (non-attenuation mode) changes dependent upon the frequency of an entered signal.
As is mentioned above, since the conventional step attenuators have an attenuation setting error, using them for the purpose of providing a broad-band gain control causes low accuracy in gain settings. It is noted that we define the attenuation setting error to mean the error between the attenuation value, which is decided based upon the difference between the transmission losses in the respective through-mode and attenuation mode, and he default attenuation value.
The attenuation setting error may be a main factor in reducing the attenuation accuracy. Therefore, it is important to decrease the error over the broad band.